Backup operations for client data on a storage network are often performed on streams of data which are managed by subclients and sent to a backup drive or media device. Typically, on a given stream, only one sub client can perform a backup at any given time. The concurrency limit for the number of backups that can go to a stream at any given time is one. Indirectly this means that only one backup can be sent to a media or drive at any point.
This limitation has a major drawback. With tape speeds in media increasing and the difference between disk speed and tape speed widening, the tape throughput is being throttled by the slower disks. This becomes a major issue in a large enterprise where there are many clients with slow, under performing disks with large amounts of data that need to be backed up in a fixed backup window. The only way the backup window can be met is by backing up these clients, each to a different piece of media in different drives. This increases the hardware requirement costs. This also can create a “shoe shining” effect in which the tape is driven back and forth since drive capacity is under-utilized at certain times.
Tape capacity is also growing and data from multiple clients can actually fit on a single piece of media especially if the backup being performed is an incremental backup. Scattering data across many pieces of media is a tape-handling nightmare for backup administrators.